In recent years, the use of balloon catheters to dilate body passages has become a popular method of medical treatment. The most common such use is angioplasty in which a balloon catheter is used to dilate a coronary artery by collapsing or compressing plaque. Another relatively new use for balloon catheters is uroplasty. This treatment relieves urinary obstruction caused by the swelling of the prostate.
In the past, transurethral resections (TUR) were commonly performed to remove sections of the prostate gland in order to relieve urinary obstruction at the bladder neck and in the prostatic urethra. Uroplasty involves inserting a balloon into the prostatic urethra (the section of the urethra that passes through the prostate gland--located distal to the neck of the urinary bladder and proximal to the urethral valve or sphincter) and inflating the balloon for 1 to 30 minutes to dilate the prostatic urethra and bladder neck.
At the present time, state of the art uroplasty involves using a 25mm balloon on a 12 to 18 French catheter. The procedure is usually performed under fluoroscopy to enable the physician to visualize placement of the balloon section of the catheter proximal to the external sphincter. Careful placement is essential in order to prevent dilating and damaging the sphincter. The balloon catheters usually contain radiopaque markers to enable the visualization of balloon location under fluoroscopy; however, urologists prefer to visualize the urinary tract through fiber optic instrumentation using a special endoscope, more specifically a cystoscope or a cysto-urethroscope.
There is a need for a uroplasty balloon catheter that can be introduced through a cystoscope, or the like, and which permits the urologist to directly visualize the prostatic urethra and the placement of the balloon without the need for fluoroscopy.
In addition, it has recently been found that better results are obtained when the prostate is dilated with a balloon that expands to approximately 35mm instead of the normal 25mm. Although balloon catheters which can inflate and dilate to 35mm can be made, it has not been possible to fabricate a catheter with a balloon of 25 mm much less 35 mm inflated diameter that will fit through the 12F working channel of the bridge of a rigid cystoscope.
Those skilled in the art of making balloon catheters recognize that a common ratio of the balloon's expanded outer diameter (OD) to the balloon's collapsed outer diameter or "leg" OD is generally in the range of 4 to 6. For example, a state of the art 25mm uroplasty balloon on a 14F catheter would have a balloon-to-leg ratio of 25.times.3.14/14 =5.6, and the ranges for angioplasty balloons are generally in the range of 4 to 5. Therefore, it can be appreciated that a 35mm balloon on a 12F catheter would require a ratio of 35.times.3.14/12=9.5, which is extremely difficult to accomplish. This large balloon size introduces an additional difficulty in that even if the non-balloon portion of a 12F catheter body were to fit into the working channel of the sheath of a cystoscope, it would be extremely difficult to fold or wrap a 35mm balloon with its large surface area down sufficiently small on a 12F catheter body to fit through the 12F working channel of the bridge of the cystoscope.
It would be advantageous to have a balloon catheter in which the balloon could be folded or collapsed more compactly to further reduce its deflated profile.
Fabrication techniques, preferably blowing technologies, exist that enable inflated balloon-to-leg ratios on the order of 9 and more. However, as previously stated although balloon catheters with such favorable ratios can be made, the problem of inserting the balloon section into and through the 12F working channel of the bridge of a conventional cystoscope still remains a problem. Although with proper folding and construction of the leg of the balloon, the balloon might conceivably be forced through the working channel in the bridge, which includes a bend and a stainless steel stopcock, the effort could damage the thin-walled balloon if the fit is too snug.
Obviously, it would be advantageous to have a uroplasty catheter with a 35mm balloon and a method of introducing such a catheter into a patient using an endoscope.